OFFSET
1,1
COMMENTS
The sequence starts with 1999290307891606810 and continues for another 125 terms (none previously reported, including the first term) each turning into a 119-digit palindrome after 261 steps until the sequence ends with 1999291987030606810. The distance between successive terms in the reported sequence has 9000000 as the greatest common divisor. No further numbers beyond 1999291987030606810 belonging to the same sequence are known, discovered or reported. Moreover, 1999291987030606810 is currently the largest discovered "most delayed palindrome". The sequence was found empirically using computer modeling algorithms.
It is only a conjecture that there are no further terms. - N. J. A. Sloane, Jan 24 2017
REFERENCES
Popular Computing (Calabasas, CA), The 196 Problem, Vol. 3 (No. 30, Sep 1975).
LINKS
Sergei D. Shchebetov, Table of n, a(n) for n = 1..126
Jason Doucette, World Records
Yutaka Nishiyama, Numerical Palindromes and the 196 Problem, International Journal of Pure and Applied Mathematics, Volume 80 No. 3 2012, 375-384.
R. Styer, The Palindromic Conjecture and the Fibonacci Sequence, Villanova University, 1986, 1-11.
C. W. Trigg, Palindromes by Addition, Mathematics Magazine, 40 (1967), 26-28.
C. W. Trigg, More on Palindromes by Reversal-Addition, Mathematics Magazine, 45 (1972), 184-186.
Wikipedia, Lychrel Number
196 and Other Lychrel Numbers, 196 and Lychrel Number
EXAMPLE
Each term requires exactly 261 steps to turn into a 119-digit palindrome, the last term of A281509, and is separated by some multiples of 9000000 from the adjacent sequence terms.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Andrey S. Shchebetov and Sergei D. Shchebetov, Jan 24 2017
STATUS
approved